Trade ministers from the United States and 11 other countries opened talks Saturday in an attempt to meet a US deadline to forge a trans-Pacific trade pact before the end of the year.

However, analysts said an agreement on the proposed Trans-Pacific Partnership (TPP) was unlikely to be reached during the four-day meeting.

The TPP is being negotiated by 12 nations -- Australia, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore, the United States and Vietnam -- that together make up 40 percent of the global economy.

Washington has spearheaded the secretive talks, which have been denounced by non-government groups for their alleged lack of transparency.

President Barack Obama has hailed the TPP as a centrepiece of renewed US engagement in Asia, saying it contains market-opening commitments that go well beyond those made in other free-trade accords.

US Vice President Joe Biden, who is in South Korea on the final leg of a Northeast Asia tour, said that more work would be needed to secure a deal before the year-end deadline.

"We have to end the bureaucratic hurdles that close off trading in key sector trading like autos and agriculture," Mr Biden said.

While in Japan on Tuesday, Biden pushed Tokyo to step up efforts to open its auto and farm markets.

Japan and US protect sensitive industries

Foreign automakers have long complained that Japanese authorities erect huge barriers to its lucrative market and Tokyo has insisted it will never lift all tariffs on sensitive farm products amid strong domestic opposition to opening up the sector.

TPP negotiators have also been divided over patent issues, in particular on medicines.

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